docs: def dataframe(self):
          """
          Returns a pandas DataFrame where each row is a representation of the
          Game class. Rows are indexed by the boxscore string.
          """
          frames = []
          for game in self.__iter__():
              # If both the runs scored and allowed are None, the game hasn't
              # been played yet, and the data should not be included in the
              # DataFrame.
              if game._runs_scored is None and game._runs_allowed is None:
                  continue
              frames.append(game.dataframe)
          if frames == []:
              return None
          return pd.concat(frames)